1. Field of the Invention
This invention relates to molten metal mixing. More particularly, the invention relates to the mixing together of several streams of molten metal by transfer of momentum to form a molten metal alloy.
2. Description of the Related Art
The production of aluminum base alloys has become of increasing interest due to the combination of lightweight and high strength which such an alloy can be made to possess. However, the formation of some aluminum base alloys is significantly more difficult than that of other aluminum base alloys due to the rapid adsorption of hydrogen gas by some alloys such as, for example, aluminum-lithium alloys; reaction of some alloys with refractory linings in the furnace; and composition gradients in the cast ingot due to the propensity of some alloying metals such as, for example, lithium to oxidize during processing of the molten alloy after the addition of the alloying metal.
Attempts have been made to remedy these problems by, for example, adding the lithium to the melt after degassing of the molten aluminum. The lithium is introduced into the molten aluminum from an entrance port submerged beneath the surface of the molten aluminum to ensure faster melting and mixing with minimum oxidation of the lithium. Such an apparatus is shown in Bowman et al U.S. Pat. No. 4,556,535, assigned to the assignee of this invention.
The need for uniformity of composition usually requires mechanical stirring which may promote oxidation as well as further hydrogen absorption. The molten mixture is, therefore, preferably degassed after the mixing step to lower the impurity content of the melt by bubbling a sparging gas through the molten metal.
It would, however, be desirable to perform the mixing of the molten metal streams together in a manner which would minimize either oxidation or the introduction of impurities such as hydrogen into the mixture while efficiently mixing the molten metal streams together.